Morphometric and Morphological Study of the First Rib in the Population of Rajasthan, India: A Cross-sectional Study.

Introduction: The first rib is the shortest, most curved and atypical of all ribs. An angle is visible between the head and the tubercle at the inferior portion of the neck, which can indicate the sex of the individual when viewed in a non anatomical position. Aim: To determine the morphometric and morphological variations of the first rib in the population of Rajasthan. Materials and Methods: This cross-sectional study was conducted in the Anatomy Department of SMS Medical College, Jaipur, Rajasthan, India, from January 2023 to April 2024. A total of 90 adult human dry first ribs (45 right and 45 left) of unknown age and sex were studied. Intact right and left ribs were included, while damaged first ribs were excluded. Data were collected using a Vernier calliper and thread to measure length, height, angle, external length, internal length, shortest external length and shortest internal length. Morphological variations, such as the scalene tubercle and vascular groove, were observed. Independent samples t-tests were used to compare means between the right and left-sides and correlation analysis assessed relationships between angular orientation and anatomical dimensions. The statistical analysis was performed using Microsoft Excel 2020 and IBM Statistical Package of Social Sciences (SPSS) version 23.0. Results: The descriptive statistics for the measured variables are as follows: the mean height and length on the right-side were 6.99±3.45 cm and 26.69±2.41 cm, respectively, while on the leftside they were 7.35±2.55 cm and 26.10±2.80 cm, respectively. The angle was greater on the left-side (16.59±6.18°). Statistical analysis indicated non significant differences between all the variables of the right and left-sides (p-value >0.05), except for strong positive correlations between angle and height (Right: r-value=0.986, p-value=0.001; Left: r-value= 0.952, p-value=0.001). Conclusion: The morphometric parameters of the first rib indicate non significant differences between the right and leftsides. The strong positive correlations between angle and height have clinical significance, as they can assist in forensic and anatomical studies related to intervertical dimensions and anatomical alignment based on the angular orientation of the first rib. [ABSTRACT FROM AUTHOR]